The Elements of Geology eBook

This eBook from the Gutenberg Project consists of approximately 328 pages of information about The Elements of Geology.

Although the great earth folds were slowly raised, and no doubt eroded in their rising, they formed in all probability a range of lofty mountains, with a width of from fifty to a hundred and twenty-five miles, which stretched from New York to central Alabama.

From their bases lowlands extended westward to beyond the Missouri River.  At the same time ranges were upridged out of thick Paleozoic sediments both in the Bay of Fundy region and in the Indian Territory.  The eastern portion of the North American continent was now well-nigh complete.

The date of the Appalachian deformation is told in the usual way.  The Carboniferous strata, nearly two miles thick, are all infolded in the Appalachian ridges, while the next deposits found in this region—­those of the later portion of the first period (the Trias) of the succeeding era—­rest unconformably on the worn edges of the Appalachian folded strata.  The deformation therefore took place about the close of the Paleozoic.  It seems to have begun in the Permian, in, eastern Pennsylvania,—­for here the Permian strata are wanting,—­and to have continued into the Trias, whose earlier formations are absent over all the area.

With this wide uplift the subsidence of the sea floor which had so long been general in eastern North America came to an end.  Deposition now gave place to erosion.  The sedimentary record of the Paleozoic was closed, and after an unknown lapse of time, here unrecorded, the annals of the succeeding era were written under changed conditions.

In western North America the closing stages of the Paleozoic were marked by important oscillations.  The Great Basin, which had long been a mediterranean sea, was converted into land over western Utah and eastern Nevada, while the waves of the Pacific rolled across California and western Nevada.

The absence of tuffs and lavas among the Carboniferous strata of North America shows that here volcanic action was singularly wanting during the entire period.  Even the Appalachian deformation was not accompanied by any volcanic outbursts.

LIFE OF THE CARBONIFEROUS

Plants.  The gloomy forests and dense undergrowths of the Carboniferous jungles would appear unfamiliar to us could we see them as they grew, and even a botanist would find many of their forms perplexing and hard to classify.  None of our modern trees would meet the eye.  Plants with conspicuous flowers of fragrance and beauty were yet to come.  Even mosses and grasses were still absent.

Tree ferns lifted their crowns of feathery fronds high in air on trunks of woody tissue; and lowly herbaceous ferns, some belonging to existing families, carpeted the ground.  Many of the fernlike forms, however, have distinct affinities with the cycads, of which they may be the ancestors, and some bear seeds and must be classed as gymnosperms.

Dense thickets, like cane or bamboo brakes, were composed of thick clumps of Calamites, whose slender, jointed stems shot up to a height of forty feet, and at the joints bore slender branches set with whorls of leaves.  These were close allies of the Equiseta or “horsetails,” of the present; but they bore characteristics of higher classes in the woody structures of their stems.

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The Elements of Geology from Project Gutenberg. Public domain.
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